A typical conventional method for forming solder bumps is to apply a solder paste on pad electrodes of a substrate by using a screen printing method or a dispensing method, and to reflow the solder paste by applying heat. In such case, creamlike solder has been used as the solder paste.
As a reflow device for performing the aforementioned solder bump forming method, there is known a device with a structure that directly places a substrate on a panel heater and heats the substrate by thermal conduction from the panel heater (conventional case 1). However, this reflow device has such a defect that thermal distributions on the substrate become ununiform because of a slight curvature or unevenness of the substrate. There is also known a reflow device which heats a substrate by heat radiation from a panel heater through providing a space between the panel heater and the substrate (conventional case 2). However, this reflow device has such a defect that the heating power for heating the substrate by the panel heater is insufficient. As a reflow device for overcoming the defects of the conventional examples 1 and 2, a reflow device that heats a substrate by applying hot air thereto has been developed (conventional case 3, e.g. Patent Document 1). The reflow device disclosed in Patent Document 1 is constituted to provide a space between hot-air outlets and a substrate, and to heat the substrate by applying hot air from the top and bottom of the substrate so that the substrate can be uniformly heated with a sufficient heating power.    Patent Document 1: Japanese Unexamined Patent Publication H5-92257